DUBOW ADAM (Gen Counsel & Secretary) sold 8.1% of their position (6.39K shares) of DAY ONE BIOPHARMACEUTICALS, INC. on the open market

Open‑market sale worth $74.2K — a moderate reduction. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 1 sale

DUBOW ADAM

Filed: 2/18/2026ACC: 0001744507-26-000004

InsiderDUBOW ADAMCIK 1744507

→

IssuerDAY ONE BIOPHARMACEUTICALS, INC.CIK 1845337

Officer· Gen Counsel & Secretary

Since Feb 2026

-6.39K

Net shares

Net seller

$74.2K

Total sold

Open market trades

0B · 1S

Total transactions

16.46K acquired · 22.86K disposed

Non-Derivative Transactions6

Common Stock

Direct

M · Option Exercise

+2.96K

Price / share

—

Trade value

—

% of position

4.7%

2/15/2026

62.63K→65.59K

Common Stock

Direct

M · Option Exercise

+1.75K

Price / share

—

Trade value

—

% of position

2.7%

2/15/2026

65.59K→67.34K

Common Stock

Direct

M · Option Exercise

+3.69K

Price / share

—

Trade value

—

% of position

5.5%

2/15/2026

67.34K→71.03K

Common Stock

Direct

M · Option Exercise

+3.69K

Price / share

—

Trade value

—

% of position

5.2%

2/15/2026

71.03K→74.71K

Common Stock

Direct

M · Option Exercise

+4.38K

Price / share

—

Trade value

—

% of position

5.9%

2/15/2026

74.71K→79.09K

Common Stock

Direct

S · Sale

−6.39K

Price / share

$11.60

Trade value

$74.19K

% of position

8.1%

2/17/2026

79.09K→72.69K

Total

Net shares

+10.07K

Net value

-$74.19K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	2/15/2026	M · Option Exercise	+2.96K	—	—	4.7%	62.63K	65.59K
Common Stock Direct	2/15/2026	M · Option Exercise	+1.75K	—	—	2.7%	65.59K	67.34K
Common Stock Direct	2/15/2026	M · Option Exercise	+3.69K	—	—	5.5%	67.34K	71.03K
Common Stock Direct	2/15/2026	M · Option Exercise	+3.69K	—	—	5.2%	71.03K	74.71K
Common Stock Direct	2/15/2026	M · Option Exercise	+4.38K	—	—	5.9%	74.71K	79.09K
Common Stock Direct	2/17/2026	S · Sale	−6.39K	$11.60	$74.19K	8.1%	79.09K	72.69K
Total			+10.07K		-$74.19K

Derivative Transactions5

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

2.96K shares

−2.96K

Strike price

Held after

8.89K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

1.75K shares

−1.75K

Strike price

Held after

5.25K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.69K shares

−3.69K

Strike price

Held after

25.82K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.69K shares

−3.69K

Strike price

Held after

40.56K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

4.38K shares

−4.38K

Strike price

Held after

65.63K

Exercisable

—

2/15/2026

Security	Converts To	Date	Type	Shares	Exercisable	Held After
Restricted Stock Unit (RSU) Direct	Common Stock2.96K shares	2/15/2026	M · Option Exercise	−2.96K	—	8.89K
Restricted Stock Unit (RSU) Direct	Common Stock1.75K shares	2/15/2026	M · Option Exercise	−1.75K	—	5.25K
Restricted Stock Unit (RSU) Direct	Common Stock3.69K shares	2/15/2026	M · Option Exercise	−3.69K	—	25.82K
Restricted Stock Unit (RSU) Direct	Common Stock3.69K shares	2/15/2026	M · Option Exercise	−3.69K	—	40.56K
Restricted Stock Unit (RSU) Direct	Common Stock4.38K shares	2/15/2026	M · Option Exercise	−4.38K	—	65.63K